1. Field of the Invention
This invention relates to a method for producing embossing plates, in particular steel intaglio printing plates.
2. Description of Related Art
For producing embossing plates, in particular steel intaglio printing plates, as are usually employed for printing high-quality printed products such as papers of value, bank notes or the like one has hitherto resorted to having the embossing plates produced in an elaborate method by an artist. A picture motif made available to the artist is converted into a line pattern whereby lines of different width, depth and a different number per unit area represent the gray levels of the original. Using a chisel, the artist brings this motif in time-consuming hand labor into the metal plate, for example steel or copper. The thus produced plates are characterized by their high quality with respect to use in steel intaglio printing. However the possibilities of correction are extremely low for the artist during production of the plate. If this original plate is damaged or lost, no identical plate can be produced since each plate is an individual production.
It is also known to perform the engraving of a printing cylinder by machine. As described in EP 0 076 868 B1 for example, cups are brought into the printing form which represent the gray level value of a master depending on their screen width and engraving depth. Light tones and tone-dependent changes in the master are produced by varying the focal value of the electron beam in the printing form, whereby cups of different volume can arise.
From DE 30 08 176 C2 it is also known to use a laser for engraving a printing cylinder. An original is scanned and the resulting signal used via an analog-to-digital converter for controlling the laser with which engraved cups of defined depth and extension are brought into the printing cylinder.
When the original is broken down into gray-level values represented on the printing plate by cups, the essential components necessary for steel intaglio printing are lost, since this technique is only able to transfer ink to the print carrier point by point. Steel intaglio printing, however, is characterized by the fact that a continuous linear printing pattern tangible with the inking is transferred to the print carrier, characterized in particular by its filigreed design.